1. Field of the Invention
This invention relates to an electron-emitting device, an electron source, an image display apparatus, and a manufacturing method of an electron-emitting device.
2. Description of the Related Art
In order to apply an electron-emitting device to an image display apparatus, an enough emission current to make a phosphor luminous with sufficient luminance is required. Additionally, an electron beam applied to the phosphor is required to have a small diameter in order to realize a high definition display. Further, the ease of production of the electron-emitting device is important.
In order to make the phosphor luminous with sufficient luminance, an emission current density may be increased.
As a field emission (FE) type electron-emitting device, there is a Spindt-type electron-emitting device, for example. In general, the Spindt-type electron-emitting device has a microchip as an electron-emitting member and emits electrons from the top end. The Spindt-type electron-emitting device generally has plural microchips per one device in order to increase the emission current density. In some cases, a structure for focusing an electron beam between a gate electrode and a cathode electrode may be formed. Such a structure is disclosed in, for example, U.S. Pat. No. 5,798,604.
Meanwhile, as the field emission (FE) type electron-emitting device, there is an electron-emitting device in which at least one portion of a thin film provided on a cathode electrode is exposed in an opening of a gate electrode and an insulating layer to perform electron emission from the exposed portion.
A material with a low work function is used as the electron emission material used in the thin film, whereby an electron-emitting device which can emit electrons without using a microchip can be formed. Further, the electron-emitting devices emit electrons from the surface of the thin film, and therefore, concentration of an electric field is more difficult to occur than the electron-emitting device using the microchip and has a long life.
However, the emission current density of the above thin film is small, and therefore, in order to obtain more emission current, the exposed area of the thin film is required to be increased, or the electric field is required to be effectively applied on the surface of the thin film.
In general, as with the Spindt-type electron-emitting device, plural openings (each opening of the gate electrode and the insulating layer) are provided in one electron-emitting device, and the opening of the insulating layer is formed to be larger than the opening of the gate electrode. However, the formation of plural openings (each opening of the gate electrode and the insulating layer) results in the increasing of the size of the electron-emitting device.